A conventional powered device connected with an Ethernet, such as an IP phone, web camera, wireless bridge, cash register, or secure accessing and monitoring system etc., needs battery or power cord and power socket disposed on the terminal network device for power supply. A better way to do is to supply the power while transmitting data to the powered device connected with the Ethernet. And the Power over Ethernet (PoE) technology provided by the IEEE802.3af standard is capable of transmitting power and data to the powered device connected with the Ethernet at the same time.
Please refer to FIG. 1, PoE is a kind of technology applied to Ethernet that allows the power and data of a power sourcing equipment 1 (such as Ethernet switch, router, hub, other network switch, and mid-span PSE etc., hereinafter abbreviated as PSE) to be transmitted to a powered device 21, 22 or 23 complied with PoE through twisted pair.
Please refer to FIG. 2, if a mid-span PSE, a kind of the power sourcing equipment 1 stated above, is disposed between a conventional remote network device 10 not complied with PoE and a powered device 21, 22 or 23 complied with PoE, the network signals of the conventional remote network device 10 may be received through the mid-span PSE, and meanwhile, the power and data may be transmitted from the mid-span PSE to the powered device 21, 22 or 23, thus the objectives of PoE may be achieved. Therefore, while employing PoE, the powered device 21, 22 or 23 not suitable for extra power cord may be powered and data may be transmitted normally without altering the structure of the Ethernet.
However, the conventional powered device may be damaged if it is provided with high voltage (such as 48V) from the power sourcing equipment 1. Hence, for the safety of the conventional powered device, the power sourcing equipment 1 is equipped with a “discovery procedure” to find out that whether the powered device connected with the power sourcing equipment 1 is complied with PoE, thereby prevents the conventional powered device from being damaged for misconnection with the power sourcing equipment 1.
However, in the case that the power sourcing equipment 1 is provided with 48 “PoE port”, the circuit of the power sourcing equipment 1 must comprise twelve sets of Ethernet power supply control unit 3. Please refer to FIG. 3, each set of Ethernet power supply control unit 3 comprises one Ethernet power supply controller 30 and four individual Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) 32, 33, 34 and 35 and controls four ports. For the power sourcing equipment 1 to be equipped with a “discovery procedure”, the circuit design of the power sourcing equipment 1 will be quite complicated which leads to higher manufacturing cost. Besides, please refer to FIG. 4, PoE now primarily uses RJ-45 connector 4 as the “PoE port” which is provided with the first to the eighth conductors 41 to 48 from the left to the right wherein the first to the third conductors 41 to 43 and the sixth conductor 46 are utilized to transmit network signals while the fourth, fifth, seventh, and eighth conductors 44, 45, 47 and 48 are utilized to transmit other signals or power. All of the conductors 41 to 48 of the RJ-45 connector 4 may not be able to support other application even when there's a need for transmission of other signals or in the case that PoE is not employed. Thus, developing a new technology for the problems of complicated circuit design, high manufacturing cost and lack of extra conductor has become an issue with great importance.